Multi-intersection traffic control system

ABSTRACT

A master traffic control system including both methods of and apparatus for selecting, from a plurality of pre-recorded programs, a particular program to control the energization of traffic lights at a number of intersections. The program may be chosen in response to various traffic parameters computed from signals supplied by vehicle detectors, or by the time of day, as determined by selective programming of the master controller. The traffic parameters are represented as an analog voltage cumulatively variable with changes in traffic activity, and the traffic control program may be selected in accordance with various selected averages, ratios and ranges of the computed parameters. Novel circuitry is also provided for accomplishing various functions in the master controller, such as monitoring the detector inputs, providing the analog output voltage representing the traffic parameters, averaging the voltages, etc. Various indicating devices receive outputs from control system values and operations to provide visual displays and printed records of traffic parameter values, program identifications, etc.

United States Patent 1 1 Meyer et a1.

[ MULTI-INTERSECTION TRAFFIC CONTROL SYSTEM [75] Inventors: Jerome W. Meyer, Santa Clara;

Phillip A. Annen, Sunnyvale, both of Calif.

[73] Assignee: The Singer Company, Binghamton,

[22] Filed: Nov. 8, 1971 [21] Appl. No.: 196,312

Related U.S. Application Data [63] Continuation-impart of Ser. No. 166,915, July 28,

1971, abandoned.

[52] U.S. Cl. 340/35 [51] Int. Cl G08g 1/08 [58] Field of Search 340/35, 31 A, 40

[56] References Cited UNITED STATES PATENTS 3,239,653 3/1966 Barker 235/150.24 3,254,324 5/1966 Casciato et a]. 340/ 3,397,306 8/1968 Auer 235/150.24 3,482,208 12/1969 Auer et al.... 340/35 3,675,196 7/1972 Molloy 340/ 1 June 18, 1974 Primary Examiner-William C. Cooper Attorney, Agent, or Firm-J. Ronald Richbourg; James C. Kesterson [5 7 ABSTRACT A master traffic control system including both methods of and apparatus for selecting, from a plurality of pre-recorded programs, a particular program to control the energization of traffic lights at a number of intersections. The program may be chosen in response to various traffic parameters computed from signals supplied by vehicle detectors, or by the time of day, as determined by selective programming of the master controller. The traffic parameters are represented as an analog voltage cumulatively variable with changes in traffic activity, and the traffic control program may be selected in accordance with various selected averages, ratios and ranges of the computed parameters. Novel circuitry is also provided for accomplishing various functions in the master controller, such as monitoring the detector inputs, providing the analog output voltage representing the traffic parameters, averaging the voltages, etc. Various indicating devices receive outputs from control system values and operations to provide visual displays and printed records of traffic parameter values, program identifications, etc.

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1. A method of changing timing of energization of a plurality of traffic signal devices located throughout an area of related traffic movement, wherein the timing of energization of said signal devices is controlled by a timing apparatus at selected locations in said area said method comprising: a. storing a plurality of different data blocks representative of time duration in a storage medium for transmission in the form of electrical signals commensurate with the time duration in any of said data blocks; b. electrically indicating the presence of vehicles at selected locations in said area; c. computing a traffic flow parameter value derived from the indication of vehicle presence at one or more of said selected locations over a selected time period; d. generating a time-related analog signal having a magnitude varible in response to the value of said computed parameter; e. selecting one of said data blocks as a function of said analog signal magnitude; and f. transmitting said selected data block to said timing apparatus for changing the timing of energization of said traffic signal devices to that of said selected data block.
 2. The invention according to claim 1 and further including the steps of establishing a plurality of discrete ranges into which the value of said analog signal magnitude may fall, determining the one of said ranges into which said value does fall, and selecting one of said time duration data blocks for transmission in accordance with said one range.
 3. The invention according to claim 2 wherein digital signals are provided to indicate the range into which the value of said analog signal magnitude falls.
 4. The invention according to claim 1 wherein said parameter is traffic density.
 5. The invention according to claim 4 wherein vehicle presEnce is indicated by switching an electrical indicating signal between a first and a second level, respectively, when vehicles are and are not in one of said selected locations, whereby traffic density at said one location over a selected time period may be computed by calculating the percentage of said time period for which said indicating signal is at said first level.
 6. The invention according to claim 5 and further including the step of averaging a plurality of said indicating signals from a corresponding plurality of said selected locations to provide an average value of traffic density over said plurality of locations.
 7. The invention according to claim 1 and further including the steps of electrically indicating the presence of vehicles in two separate groups of selected locations in said area, computing separate parameters and generating separate analog signals for each of said groups, and selecting a separate one of said time duration data blocks for controlling energization of said traffic signal devices in each of said groups of locations.
 8. The invention according to claim 1 and further including the step of computing an additional parameter value commensurate with said vehicle presence indications, the additional parameter being related to but different than the first-mentioned parameter, and calculating the ratio of one of said parameter values to the sum of the two parameter values, and selecting said time duration data block for transmission as a function of said ratio.
 9. The invention according to claim 8 and further including the steps of establishing a plurality of discrete ranges into which the value of said ratio may fall, determining the one of said ranges into which said ratio does fall, and selecting one of said data blocks for transmission in accordance with said one range.
 10. The invention according to claim 1 and further including the step of selecting one of said data blocks for transmission at a preselected time of day, while inhibiting transmission of any of said data blocks selected as a function of said analog signal magnitude.
 11. A method of monitoring input signals from a plurality of vehicle presence detectors at selected locations in a traffic sampling area, said method comprising: a. providing a first indication signal level during the time a vehicle is present at any one of said selected locations; b. providing a second indication signal level during the time no vehicle is present at any one of said selected locations; c. periodically determining whether said indication signal level has changed between said first and second levels during the period; and d. providing a third indication signal level in response to a determination that no change between said first and second levels has occurred during said period.
 12. The invention according to claim 11 and further including the step of calculating from said indication signals a traffic parameter based on the presence of vehicles at said selected locations.
 13. The invention according to claim 12 wherein the calculation of said parameter is based only on said first and second indication signal levels, any third indication signal levels being disregarded.
 14. The invention according to claim 13 wherein separate indication signals are provided from each of a plurality of vehicle presence detectors at different selected locations, and further including the step of averaging said indication signals in calculating said parameter.
 15. The invention according to claim 11 wherein said period may be selectively varied.
 16. In a multi-intersection traffic control system including at preselected locations, a. traffic signal devices; b. vehicle presence detectors; and c. intersection controllers having a timing apparatus to control energization of said signal devices in predetermined cycles, wherein the improvement comprises a master control apparatus for accepting actuation signals from said detectors and providing time duratIon data for changing said predetermined cycles of said timing apparatus, said control apparatus further including: d. storage means for a plurality of discrete programs of time duration data, each associated with said predetermined cycles; e. computer means for calculating from said vehicle actuation signals at least one parameter having a value derived therefrom, and representing said parameter by an analog signal; f. first selection means responsive to at least one of said analog signals to select one of said discrete programs in accordance with the value thereof; and g. means for transmitting the time duration data of said selected program to said timing apparatus to thereby change the predetermined cycles for controlling the energization of said signal devices.
 17. The invention according to claim 16 wherein said storage means comprises a punched tape and said transmitting means comprises means for generating electrical signals related to the position of holes punched in said tape.
 18. The invention according to claim 16 and further including clock means for generating electrical pulses in predetermined time sequences and second selection means to select and transmit the data of one of said discrete programs in accordance with a preselected combination of said pulses and to inhibit the simultaneous transmission of programs selected by said first selection means.
 19. The invention according to claim 18 and further including input circuitry for receiving said vehicle actuation signals and supplying same to said computer means, and means for periodically determining whether any of said vehicle presence detectors have failed to register a change in their respective actuation signals during a preselected time interval.
 20. The invention according to claim 19 wherein selected pulses from said clock means are applied to said input circuitry to establish said time interval.
 21. The invention according to claim 20 and further including means for inhibiting transmission to said computer means of said vehicle actuation signals from detectors which have failed to register a change in actuation signals during one of said time intervals.
 22. The invention according to claim 18, wherein said first selection means includes: a. a number N of program selection means responsive to predefined amplitudes of said analog signals; and b. means for rendering inoperative N-1 of said program selection means, said means for rendering inoperative being controlled in accordance with preselected states of said clock means, whereby one of said discrete programs is selected by the operative program selection means.
 23. The invention according to claim 22 wherein said meters include means providing a permanent record of continuous variations in said parameters.
 24. The invention according to claim 16 and further including circuit means for determining into which one of a plurality of preselected ranges of values the value of said analog signal falls, and said first selection means is reponsive to said one range to select said program in accordance therewith.
 25. The invention according to claim 16 wherein said computer means is adapted to compute first and second parameter values associated with related but different groups of said vehicle actuation signals.
 26. The invention according to claim 25 wherein said first and second parameter values are averaged in arriving at said analog signal.
 27. The invention according to claim 25 and further including means for computing the ratio of said first parameter value to the sum of said first and second parameter values.
 28. The invention according to claim 16 and further including a plurality of output meters for visually indicating the value of one or more of said parameters.
 29. The invention according to claim 16 and further including means for providing a permanent record of the identification of selected blocks of time duration data transmitted to said timing apparatus toGether with the time and date of transmission thereof.
 30. In a traffic control system, an apparatus for receiving input signals from a plurality of sensing devices, said input signals changing between high and low levels in response to random actuations of said sensing devices, said apparatus comprising, in combination: a. means providing a first level output signal in response to a high level input signal; b. means providing a second level output signal in response to a low level input signal; c. timing means periodically providing electrical timing signals to establish repetitive time intervals; and d. means providing a third level output signal in response to one of said timing signals when said input signal has remained at one of said high and low levels during said time interval preceding said one timing signal.
 31. The invention according to claim 30 wherein said apparatus receives said input signals from a plurality of separate vehicle presence detectors which provide high and low signals in response to the presence or non-presence of a vehicle at the respective detector locations.
 32. The invention according to claim 30 and further including means for selectively varying the duration of said timing intervals.
 33. The invention according to claim 30 and further including bistable switching means and gating means, said bistable means being turned on by said timing signals and off by said input signals, and said gating means being enabled by a previously established on state of said bistable means to pass one of said timing signals, said third level signal being provided in response to the passing of one of said timing signals by said gating means.
 34. The invention according to claim 33 wherein said bistable means comprises a flipflop having said input signals as a set input and said timing signals as a reset input.
 35. The invention according to claim 34 and further including electronic latch means intermediate of said flipflop and gating means and the output of said apparatus. 